In the tobacco industry, a cartoning machine is supplied with a succession of packets of cigarettes, which are laid flat one on top of the other to form a succession of stacks, each comprising a given number of packets. The stacks are formed into orderly groups, each of which comprises a given number of side by side stacks, and forms the content of a carton obtained by means of a packaging operation wherein a sheet or blank of packaging material is folded about the relative group. Prior to performing the packaging operation, it is often necessary or convenient to turn the stacks over through 90° so that the packets in the groups are positioned on edge.